1. Field of the Invention
The present invention relates to a laminated glass sheet for a windshield with a transparent conductive film for an electric heating function and a heat shielding function. In particular, the present invention relates to a laminated glass sheet for a windshield that enables ITS (Information Technology System) communication such as ETC (Electronic Toll Collections) and VICS (Vehicle Information and Communication System).
2. Description of the Related Art
For example, JP7 (1995)-309210A discloses a heating device for electrically heating a windshield for an electric automobile, which includes a transparent conductive film and bus-bars on upper and lower sides of the windshield. This heating device is provided for the purpose of removing a frost or a fog generated on the windshield. The transparent conductive film is usually provided at least in a region corresponding to a field of view of the windshield to ensure safety driving.
In the case of using a transparent conductive film containing a metal layer such as a silver (Ag) layer, a heat-shielding function as well as a heating function is obtained. However, the conductive film containing a metal film provides an electromagnetic radiation shielding function. This makes it difficult to conduct communication such as ETC and VICS.
JP8 (1996)-210042A discloses, as a windowpane capable of transmitting an electromagnetic radiation, a windowpane having a reflection ability and/or an absorption ability of an electromagnetic ray, except for a predetermined region for transmitting an electromagnetic signal.
JP8 (1996)-250915A discloses, as a glass sheet for an automobile having a conductive layer, a glass sheet for an automobile covered with a transparent conductive layer having slit-shaped gaps with a length represented by the function of a microwave radiation wavelength.
However, in JP8 (1996)-210042A and JP8 (1996)-250915A, a region for transmitting an electromagnetic ray is provided in a field of the driver""s view. Therefore, the region tends to makes the heat-shielding function and the electric heating function insufficient.
The present invention provides a laminated glass sheet for a windshield that includes at least two glass sheets, at least one thermoplastic resin film provided between the at least two glass sheets, and a transparent conductive film and bus-bars for supplying electric power to the transparent conductive film. The transparent conductive film and the bus-bars are formed on a surface of one of the glass sheets. The bus-bars include a first bus-bar arranged along an upper end of the laminated glass sheet, and a second bus-bar arranged along a lower end of the laminated glass sheet. The first bus-bar includes a protruding portion that extends toward the second bus-bar. In other words, the first bus-bar includes an inset that extends toward the second bus-bar. The transparent conductive film is not formed in a concave portion that is formed by the protruding portion.
The concave portion enables the ITS communication. The transparent film may be free from an opening for transmitting an electromagnetic ray. Thus, a heat-shielding function and/or an electric heating function can be obtained in the whole area for a driver""s view.